Both in WindowsXP and Windows7, German language
I had an installation of LO 3.4.0, spell check working fine.
After update to 3.4.1RC1 (i.e. installing over the existing installation to preserve settings and add-ons), spell check does not work any more.
Looking in the Language settings / Linguistik shows that the language modules have disappeared ("Sprachmodule" is empty).
*** This bug has been marked as a duplicate of bug 37195 ***